Fluorophosphate-base laser glasses

ABSTRACT

A fluorophosphate-base laser glass having a low non-linear refractive index coefficient and a low liquid phase temperature and comprising a glass composed of 5 to 25% 1/2P 2  O 5  and the remainder of metal fluorides and 0.01 to 3% 1/2Nd 2  O 3  being incorporated into the glass, and more particularly a fluorophosphate-base laser glass comprising 5 to 25% 1/2P 2  O 5 , 20 to 35% AlF 3 , 0 to 5% YF 3 , 22 to 55% BaF 2  +SrF 2  +CaF 2  +MgF 2 , 0 to 25% NaF+LiF+KF and 0.01 to 3% 1/2Nd 2  O 3 , all % being cationic %.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluorophosphate-base laser glass, and more particularly, it relates to an extremely stable fluorophosphate-base laser glass possessing a very low non-linear refractive index coefficient.

2. Description of the Prior Art

Heretofore, a silicate-base laser glass and a phosphate-base laser glass are known as laser glasses. Japanese patent application (OPI) No. 111,916/74 (corresponding to U.S. patent application Ser. No. 446,085 filed Feb. 26, 1974, now abandoned) discloses a silicate-base glass composed of an SiO₂ -Al₂ O₃ -SrO-Li₂ O-Na₂ O system as a laser glass suitable for high speed and repeating oscillation. Further, Japanese patent application No. 613,795/74 discloses a phosphate-base laser glass composed of a P₂ O₅ -La₂ O₃ -Al₂ O₃ -RO system as a laser glass having far higher gain as compared with the conventional silicate-base glass.

Laser glasses for nuclear fusion have recently been required to have a high grain and also a low non-linear refractive index coefficient n₂ (the refractive index coefficient proportional to the square of the intensity of the electric field applied to the laser). Japanese patent application No. 32,696/75, corresponding to U.S. patent application Ser. No. 667,756 filed Mar. 17, 1976, discloses a P₂ O₅ -Al₂ O₃ -La₂ O₃ -Y₂ O₃ -Na₂ O-Li₂ O series laser glass as a laser glass possessing a low non-linear refractive index coefficient and a high output.

However, the above-described phosphate glass still does not have a satisfactory non-linear refractive index coefficient n₂ and laser glass must have a lower n₂.

The refractive index n of a laser in a high electric field is shown by the equation

    n = n.sub.0 + n.sub.2 E.sup.2

wherein n₂ is the non-linear refractive index coefficient, E is the intensity of the applied electric field and n₀ is the refractive index coefficient in a non-laser light (non-electric) field. If the non-linear refractive index coefficient is high, the refractive index becomes higher when the laser light passes through the glass whereby self-focusing of the laser glass occurs breaking the laser glass, and, as a result, it is difficult to exhibit high output sufficiently.

As a result of extensive investigations in order to obtain a laser glass possessing a lower non-linear refractive index coefficient n₂ than that of the conventional phosphate laser glass and which is stable as a glass itself, it has now been found that in order to obtain such a glass, it is necessary to reduce the phosphate content in the glass to as low as possible and the reduction of the phosphate content can be made by substituting the glass modifiers with fluorides, and the present invention has been achieved.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a stable fluorophosphate-base laser glass having a lower non-linear refractive index coefficient.

Another object of the present invention is to provide a fluorophosphate-base laser glass comprising a glass comprising 5 to 25% 1/2P₂ O₅ and the remainder of metal fluorides and 0.01 to 3% 1/2Nd₂ O₃, all % being cationic %.

DETAILED DESCRIPTION OF THE INVENTION

Representative examples of the metal fluorides which can be used in the present invention include those of Al, Y, Ba, Sr, Ca, Mg, Na, K, Li and La. Specific examples of metal fluorides which can be used in the present invention include AlF₃, YF₃, BaF₂, SrF₂, CaF₂, MgF₂, NaF, KF, LiF and LaF₃.

A laser glass containing 5 to 25 cationic % 1/2P₂ O₅ has a sufficiently low non-linear refractive index coefficient n₂ and is a desirable glass as a laser glass for nuclear fusion from a performance standpoint. However, since the glass forming oxide (P₂ O₅) content is very small, the stability as a glass is poor. In general, laser glasses for nuclear fusion must be a large-sized mass of glass. In veiw of this, there is further provided a fluorophosphate-base laser glass comprising 5 to 25% 1/2P₂ O₅, 20 to 35% AlF₃, 0 to 5% YF₃, 22 to 55% BaF₂ +SrF₂ +CaF₂ +MgF₂, 0 to 25% NaF+KF+LiF and 0.01 to 3% 1/2Nd₂ O₃, all % being cationic %.

Each component of the laser glass of the present invention and the amount thereof are described in detail below.

If the amount of 1/2P₂ O₅ is lower than 5 cationic %, glassification does not occur, while if the amount of 1/2P₂ O₅ is higher than 25 cationic %, the non-linear refractive index coefficient n₂ increases.

The amount of AlF₃ preferably ranges from 20 to 35 cationic % in order to decrease the liquid phase temperature.

YF₃ is an effective component to stabilize the glass, and if the amount of YF₃ exceeds 5 cationic %, the effect disappears. A preferred amount of YF₃ is 0.1 to 4 cationic %.

The total amount of BaF₂, SrF₂, CaF₂ and MgF₂ is preferably 22 to 55 cationic % in order to also obtain a sufficiently stable glass.

Each of NaF, KF and LiF is an effective component to stabilize the glass and to reduce the non-linear refractive index coefficient n₂. If the total amount of NaF, KF and LiF exceeds 25 cationic %, the chemical resistance of the glass deteriorates.

LaF₃ is an optional component and does not have any specific function. LaF₃ may be generally used in an amount up to 5 cationic %.

If the amount of 1/2Nd₂ O₃ is lower than 0.01 cationic %, it becomes difficult to oscillate the laser glass at these low amounts, while if the amount of 1/2Nd₂ O₃ is higher than 3 cationic %, the liquid phase temperature is increased and also density quenching of fluorescence occurs.

In order to obtain a large-sized mass of glass, it is necessary to decrease the liquid phase temperature to as low as possible. In order to achieve this, limiting the amount of each of BaF₂, SrF₂, CaF₂ and MgF₂ to a specific amount is very effective. That is, the amount of BaF₂ preferably ranges from 2 to 12 cationic %, the amount of SrF₂ preferably ranges from 4 to 18 cationic %, the amount of CaF₂ preferably ranges from 15 to 28% and the amount of MgF₂ preferably ranges from 0 to 5%.

Of the alkali metal fluorides, NaF is particularly preferred to decrease the liquid phase temperature and the non-linear refractive index coefficient.

The presence of MoO₃, TiO₂, 1/2Nb₂ O₅ and the like is effective in preventing solarization. Each of these components can be used in an amount up to 2 cationic %, but the total amount thereof must range from 0.1 to 4 cationic %.

Moreover, according to another embodiment of the present invention, 1/2Nd₂ O₃ may be partially or completely replaced by 1/2Er₂ O₃ and/or 1/2Eu₂ O₃ as a laser oscillation component. In addition, AlF₃, YF₃, LaF₃, NaF, KF, LiF, BaF₂, SrF₂, CaF₂ and MgF₂ can be partially or completely used in the form of the phosphates or the phosphites, such as AlPO₄, YPO₄, LaPO₄, NaPO₃, KPO₃, K₃ PO₄, Li₃ PO₄, Sr(PO₃)₂, Ca₃ (PO₄)₂, Ca(PO₃)₂, Mg₂ P₂ O₇, Ba(PO₃)₂, etc. Further, the Nd₂ O₃, Er₂ O₃ and Eu₂ O₃ can be effectively added as the fluorides thereof, such as NdF₃, ErF₃ and EuF₃ respectively.

The laser glasses accordig to the present invention have a non-linear refractive index coefficient of 0.5 to 0.7×10⁻¹³ e.s.u. and a liquid phase temperature of 550° to 750° C.

Examples of laser glasses of the present invention are shown in the Table below to explain the invention in greater detail. In the Table, each component is shown in terms of cationic %, L_(T) is the liquid phase temperature (in ° C.) which is a measure of the stability of the glass to devitrification, and n₂ is the non-linear refractive index coefficient (×10⁻¹³ e.s.u.).

The abbreviation "e.s.u." means electrostatic unit.

                                      Table                                        __________________________________________________________________________     No.     1   2   3   4   5   6   7   8   9   10                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 18  18  18  13  18  18  18  18  18  18                                       M 9.95                                                                               9.96                                                                               9.96                                                                               6.45                                                                               10.16                                                                              9.93                                                                               10.16                                                                              9.96                                                                               9.96                                                                               9.96                                     W 14.68                                                                              15.52                                                                              14.87                                                                              9.56                                                                               13.49                                                                              14.03                                                                              13.78                                                                              14.87                                                                              14.38                                                                              14.43                              AlF.sub.3                                                                            C 31.72                                                                              31.72                                                                              31.72                                                                              31.72                                                                              31.72                                                                              31.72                                                                              31.72                                                                              34.98                                                                              29.98                                                                              30.98                                    M 35.06                                                                              35.09                                                                              35.09                                                                              33.93                                                                              35.81                                                                              35.06                                                                              35.81                                                                              38.69                                                                              33.17                                                                              34.27                                    W 30.62                                                                              32.37                                                                              31.00                                                                              27.60                                                                              28.13                                                                              29.25                                                                              28.73                                                                              34.20                                                                              28.29                                                                              27.39                              YF.sub.3                                                                             C 3.26                                                                               4.26                                                                               3.26                                                                               0.26                                                                               --  3.26                                                                               3.61                                                                               --  5   3                                        M 3.61                                                                               4.71                                                                               3.61                                                                               0.28                                                                               --  3.61                                                                               --  --  5.53                                                                               3.32                                     W 5.47                                                                               7.55                                                                               5.54                                                                               0.39                                                                               --  5.22    --  8.22                                                                               4.94                               LaF.sub.3                                                                            C --  1   --  --  --  --  --  --  --  --                                       M --  1.11                                                                               --  --  --  --  --  --  --  --                                       W --  2.38                                                                               --  --  --  --  --  --  --  --                                 1/2Al.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 1/2Y.sub.2 O.sub.3                                                                   C --  --  --  --  3.26                                                                               --  3.26                                                                               --  --  --                                       M --  --  --  --  1.84                                                                               --  1.84                                                                               --  --  --                                       W --  --  --  --  3.89                                                                               --  3.97                                                                               --  --  --                                 1/2La.sub.2 O.sub.3                                                                  C --  --  --  --  --  --  --  --  --  1                                        M                                     1.4                                      W --  --  --  --  --  --  --  --  --  1.84                               BaF.sub.2                                                                            C 5.76                                                                               2.76                                                                               5.76                                                                               9   8.6 7.46                                                                               8.03                                                                               6.33                                                                               6.33                                                                               6.33                                     M 6.36                                                                               3.05                                                                               6.37                                                                               9.63                                                                               9.71                                                                               8.25                                                                               9.07                                                                               7.00                                                                               7.00                                                                               7.00                                     W 11.61                                                                              5.88                                                                               11.75                                                                              16.35                                                                              15.92                                                                              14.36                                                                              15.18                                                                              12.92                                                                              12.49                                                                              12.54                              SrF.sub.2                                                                            C 7.38                                                                               4.38                                                                               7.38                                                                               18  11.02                                                                              9.57                                                                               10.29                                                                              8.11                                                                               8.11                                                                               8.11                                     M 18.15                                                                              4.85                                                                               8.16                                                                               19.25                                                                              12.44                                                                              10.59                                                                              11.62                                                                              8.97                                                                               8.97                                                                               8.97                                     W 10.66                                                                              6.69                                                                               10.79                                                                              23.42                                                                              14.02                                                                              13.20                                                                              13.94                                                                              11.86                                                                              11.45                                                                              11.51                              CaF.sub.2                                                                            C 17.28                                                                              15.28                                                                              17.28                                                                              28  25.8                                                                               22.39                                                                              24.10                                                                              18.98                                                                              18.98                                                                              18.95                                    M 19.09                                                                              16.90                                                                              19.12                                                                              29.95                                                                              29.13                                                                              24.77                                                                              27.21                                                                              21.00                                                                              21.00                                                                              21.00                                    W 15.51                                                                              14.50                                                                              15.70                                                                              22.64                                                                              21.27                                                                              19.20                                                                              20.29                                                                              17.25                                                                              16.65                                                                              16.74                              MgF.sub.2                                                                            C 5   --  --  --  --  --  --  --  --  --                                       M 5.52                                                                         W 3.58                                                                   BaO     --  --  --  --  --  --  --  --  --  --                                 SrO     --  --  --  --  --  --  --  --  --  --                                 CaO     --  --  --  --  --  --  --  --  --  --                                 MgO     --  --  --  --  --  --  --  --  --  --                                 KF      --  --  --  --  --  --  --  --  --  --                                 NaF   C 10  20  15  --  --  1   3   12  12  12                                       M 11.05                                                                              22.12                                                                              16.59       1.11                                                                               3.39                                                                               13.27                                                                              13.27                                                                              13.27                                    W 9.83                                                                               10.21                                                                              7.33                                                                               --  --  0.46                                                                               1.36                                                                               5.87                                                                               5.60                                                                               5.69                               LiF     --  --  --  --  --  5   --  --  --  --                                                             5.53                                                                           1.42                                               1/2K.sub.2 O                                                                           --  --  --  --  --  --  --  --  --  --                                 1/2Na.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 1/2Li.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 MoO.sub.3                                                                            C 0.4 1.4 0.4 --  --  0.4 --  0.4 0.4 0.4                                      M 0.44                                                                               1.55                                                                               0.44                                                                               --  --  0.49                                                                               --  0.44                                                                               0.44                                                                               0.44                                     W 0.66                                                                               2.45                                                                               0.67                                                                               --  --  0.63                                                                               --  0.67                                                                               0.65                                                                               0.64                               TiO.sub.2                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Nb.sub.2 O.sub.5                                                                  C --  --  --  --  0.4 --  0.4 --  --  --                                       M --  --  --  --  0.23    0.23                                                 W --  --  --  --  0.56                                                                               --  0.57                                                                               --  --  --                                 NdF.sub.3                                                                            C 0.2 --  --  --  --  --  --  --  --  --                                       M 0.22                                                                         W 0.46                                                                               --  --  --  --  --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1   1.2 1.2 0.02                                                                               1.2 1.2 1.2 1.2 1.2 1.2                                      M 0.55                                                                               0.66                                                                               0.66                                                                               0.01                                                                               0.68                                                                               0.66                                                                               0.68                                                                               0.66                                                                               0.66                                                                               0.66                                     W 1.92                                                                               2.45                                                                               2.35                                                                               0.03                                                                               2.02                                                                               2.23                                                                               2.18                                                                               2.36                                                                               2.27                                                                               2.28                               L.sub.T 620 652 631 674 650 621 645 673 665 633                                n.sub.2 0.65                                                                               0.62                                                                               0.66                                                                               0.70                                                                               0.69                                                                               0.65                                                                               0.68                                                                               0.60                                                                               0.67                                                                               0.63                               No.     11  12  13  14  15  16  17  18  19  20                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 18  18  18  18  18  5   19.2                                                                               25  15.18                                                                              20                                       M 10.23                                                                              10.18                                                                              10.00                                                                              9.87                                                                               10.00                                                                              7.56                                                                               10.02                                                                              14.71                                                                              8.31                                                                               11.22                                    W 14.68                                                                              14.65                                                                              14.71                                                                              14.64                                                                              14.82                                                                              3.84                                                                               11.29                                                                              22.55                                                                              12.33                                                                              12.12                              AlF.sub.3                                                                            C 29.98                                                                              30.98                                                                              32.98                                                                              32.98                                                                              32.98                                                                              34.5                                                                               20.5                                                                               20.5                                                                               31.72                                                                              31.72                                    M 34.11                                                                              35.06                                                                              36.66                                                                              30.24                                                                              36.66                                                                              35.39                                                                              22.69                                                                              24.12                                                                              34.76                                                                              35.59                                    W 28.92                                                                              29.89                                                                              31.88                                                                              31.74                                                                              32.13                                                                              30.36                                                                              20.60                                                                              21.85                                                                              30.48                                                                              30.26                              YF.sub.3                                                                             C --  --  --  2   --  2   --  2   2   2                                        M --  --  --  2.20                                                                               --  2.05                                                                               --  2.35                                                                               2.19                                                                               2.24                                     W --  --  --  3.34                                                                               --  3.16                                                                               --  3.71                                                                               3.34                                                                               3.31                               LaF.sub.3                                                                            C --  --  --  --  --  3.2 --  --  --  --                                       M --  --  --  --  --  3.28                                                                               --  --  --  --                                       W --  --  --  --  --  6.70                                                                               --  --  --  --                                 1/2Al.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 1/2Y.sub.2 O.sub.3                                                                   C 5   4   2   --  2   --  --  --  --  --                                       M 2.84                                                                               2.26                                                                               1.11                                                                               --  1.11                                                                               --  --  --  --  --                                       W 6.49                                                                               5.19                                                                               2.60                                                                               --  2.62                                                                               --  --  --  --  --                                 1/2La.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 BaF.sub.2                                                                            C 6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.44                                                                               6.44                                                                               4.40                                                                               6.44                                                                               6.44                                     M 7.20                                                                               7.16                                                                               7.03                                                                               6.96                                                                               7.03                                                                               6.01                                                                               71.2                                                                               5.15                                                                               7.05                                                                               7.22                                     W 12.76                                                                              12.75                                                                              12.78                                                                              12.72                                                                              12.87                                                                              13.30                                                                              13.50                                                                              9.80                                                                               12.92                                                                              12.83                              SrF.sub.2                                                                            C 8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.21                                                                               8.21                                                                               6.25                                                                               8.21                                                                               8.21                                     M 7.23                                                                               9.17                                                                               9.01                                                                               8.91                                                                               9.01                                                                               8.42                                                                               9.08                                                                               7.35                                                                               8.99                                                                               9.21                                     W 11.71                                                                              11.70                                                                              11.73                                                                              11.67                                                                              11.82                                                                              11.16                                                                              12.33                                                                              9.98                                                                               11.80                                                                              11.72                              CaF.sub.2                                                                            C 18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              19.05                                                                              19.05                                                                              15.25                                                                              19.05                                                                              19.05                                    M 21.59                                                                              21.47                                                                              21.09                                                                              20.86                                                                              21.09                                                                              19.54                                                                              21.07                                                                              17.94                                                                              20.80                                                                              21.37                                    W 17.03                                                                              17.02                                                                              17.06                                                                              16.78                                                                              17.19                                                                              16.10                                                                              17.78                                                                              15.13                                                                              17.02                                                                              16.90                              MgF.sub.2                                                                              --  --  --  --  --  --  --  --  --  --                                 BaO     --  --  --  --  --  --  --  --  --  --                                 SrO     --  --  --  --  --  --  --  --  --  --                                 CaO     --  --  --  --  --  --  --  --  --  --                                 MgO     --  --  --  --  --  --  --  --  --  --                                 KF    C --  --  --  --  --  20  20  5   2   1                                        M --  --  --  --  --  20.51                                                                              22.12                                                                              5.88                                                                               2.19                                                                               1.12                                     W --  --  --  --  --  12.58                                                                              13.89                                                                              3.69                                                                               1.33                                                                               0.66                               NaF   C 10  12  12  12  12  --  5   15  10  6.67                                     M 11.38                                                                              13.57                                                                              13.33                                                                              13.19                                                                              13.33                                                                              --  5.53                                                                               17.65                                                                              10.95                                                                              7.48                                     W 4.83                                                                               5.79                                                                               5.80                                                                               5.77                                                                               5.84                                                                               --  2.51                                                                               8.00                                                                               8.00                                                                               3.18                               LiF     2   --  --  --  --  --  --  --  --  --                                 1/2K.sub.2 O                                                                         C --  --  --  --  --  --  --  --  --  1.71                                     M --  --  --  --  --  --  --  --  --  0.96                                     W --  --  --  --  --  --  --  --  --  0.91                               1/2NaNa.sub.2 O                                                                      C --  --  --  --  --  --  --  5   --  --                                       M --  --  --  --  --  --  --  2.94                                                                               --  --                                       W --  --  --  --  --  --  --  1.97                                                                               --  --                                 1/2Li.sub.2 O                                                                        C --  --  --  --  --  --  --  --  2.2 --                                       M --  --  --  --  --  --  --  --  1.20                                                                               --                                       W --  --  --  --  --  --  --  --  0.38                                                                               --                                 MoO.sub.3                                                                            C 0.4 0.4 0.4 --  --  0.4 0.4 0.4 2   --                                       M 0.46                                                                               0.45                                                                               0.44                                                                               --  --  0.41                                                                               0.44                                                                               0.47                                                                               2.19                                                                               --                                       W 0.66                                                                               0.66                                                                               0.66                                                                               --  --  0.62                                                                               0.69                                                                               0.73                                                                               3.29                                                                               --                                 TiO.sub.2                                                                            C --  --  --  0.4 0.4 --  --  --  --  2                                        M --  --  --  0.44                                                                               0.44                                                                               --  --  --  --  2.24                                     W --  --  --  0.39                                                                               0.37                                                                               --  --  --  --  1.82                               1/2Nb.sub.2 O.sub.5                                                                    --  --  --  --  --  --  --  --  --  --                                 NdF.sub.3                                                                            C --  --  1.2 1.2 --  --  --  --  --  --                                       M --  --  1.33                                                                               1.32                                                                               --  --  --  --  --  --                                       W --  --  2.78                                                                               2.77                                                                               --  --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1.2 1.2 --  --  1.2 1.2 1.2 1.2 1.2 1.2                                      M 0.68                                                                               0.68                                                                               --  --  1.33                                                                               1.23                                                                               1.33                                                                               1.41                                                                               1.31                                                                               1.35                                     W 2.32                                                                               2.32                                                                               --  --  2.34                                                                               3.18                                                                               2.41                                                                               2.56                                                                               2.31                                                                               2.29                               L.sub.T 653 641 659 643 658 903 682 700 620 615                                n.sub.2 0.70                                                                               0.69                                                                               0.67                                                                               0.64                                                                               0.67                                                                               0.54                                                                               0.61                                                                               0.78                                                                               0.60                                                                               0.66                               No.     21  22  23  24  25  26  27  28  29  30                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 20  20  20  20  19  19  20  20  18  18                                       M 11.31                                                                              11.47                                                                              11.17                                                                              10.20                                                                              10.50                                                                              10.67                                                                              11.50                                                                              11.86                                                                              10.68                                                                              9.96                                     W 16.59                                                                              16.72                                                                              16.06                                                                              16.02                                                                              14.85                                                                              15.02                                                                              15.78                                                                              17.18                                                                              14.81                                                                              14.71                              AlF.sub.3                                                                            C 31.72                                                                              24.5                                                                               29.5                                                                               29.48                                                                              29.48                                                                              29.48                                                                              24.5                                                                               21.72                                                                              31.72                                                                              31.72                                    M 35.88                                                                              28.13                                                                              32.97                                                                              33.03                                                                              32.58                                                                              33.13                                                                              28.19                                                                              25.73                                                                              37.65                                                                              35.10                                    W 31.14                                                                              24.24                                                                              28.03                                                                              27.94                                                                              27.29                                                                              27.60                                                                              23.17                                                                              22.07                                                                              30.88                                                                              30.68                              YF.sub.3                                                                             C 2   --  2   1.38                                                                               --  --  --  --  2   2                                        M 2.26                                                                               --  2.23                                                                               1.55                                                                               --  --  --  --  2.37                                                                               2.21                                     W 3.41                                                                               --  3.30                                                                               2.27                                                                               --  --  --  --  3.38                                                                               3.36                               LaF.sub.3                                                                            C --  --  --  --  5   2   --  --  --  --                                       M --  --  --  5.52                                                                               2.25                                                                               --  --  --  --  --                                       W --  --  --  10.80                                                                              4.37                                                                               --  --  --  --  --                                 1/2A1.sub.2 O.sub.3                                                                  C --  5   --  --  --  --  --  10  --  --                                       M --  2.87                                                                               --  --  --  --  --  5.92                                                                               --  --                                       W --  3.00                                                                               --  --  --  --  --  6.17                                                                               --  --                                 1/2Y.sub. 2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 1/2La.sub.2 O.sub.3                                                                  C --  --  --  --  --  --  5   --  --  --                                       M --  --  --  --  --  --  2.88                                                                               --  --  --                                       W --  --  --  --  --  --  9.17                                                                               --  --  --                                 BaF.sub.2                                                                            C 3.72                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                                                               6.44                                     M 9.21                                                                               7.39                                                                               7.20                                                                               7.22                                                                               7.12                                                                               7.24                                                                               7.41                                                                               7.63                                                                               7.64                                                                               7.12                                     W 7.02                                                                               13.30                                                                              12.77                                                                              12.74                                                                              12.45                                                                              12.59                                                                              12.71                                                                              13.66                                                                              13.09                                                                              13.00                              SrF.sub.2                                                                            C 8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                                                               8.21                                     M 9.29                                                                               9.42                                                                               9.17                                                                               9.20                                                                               9.07                                                                               9.22                                                                               9.45                                                                               9.73                                                                               9.74                                                                               9.08                                     W 12.05                                                                              12.15                                                                              11.66                                                                              11.64                                                                              11.37                                                                              11.50                                                                              11.61                                                                              12.48                                                                              11.96                                                                              11.88                              CaF.sub.2                                                                            C 19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                                                              19.05                                    M 21.55                                                                              21.86                                                                              21.28                                                                              21.34                                                                              21.05                                                                              21.40                                                                              21.92                                                                              22.57                                                                              22.61                                                                              21.07                                    W 17.39                                                                              17.53                                                                              16.82                                                                              16.78                                                                              16.39                                                                              16.58                                                                              16.75                                                                              18.00                                                                              17.24                                                                              17.13                              MgF.sub.2                                                                              --  --  --  --  --  --  --  --  --  --                                 BaO   C --  --  --  --  --  --  --  --  0.68                                                                               --                                       M --  --  --  --  --  --  --  --  0.81                                                                               --                                       W --  --  --  --  --  --  --  --  1.21                                                                               --                                 SrO   C --  --  --  --  --  --  --  0.94                                                                               --  --                                       M --  --  --  --  --  --  --  1.11                                                                               --  --                                       W --  --  --  --  --  --  --  1.18                                                                               --  --                                 CaO   C --  --  --  --  --  --  3.16                                                                               --  --  --                                       M --  --  --  --  --  --  3.64                                                                               --  --  --                                       W --  --  --  --  --  --  2.00                                                                               --  --  --                                 MgO   C --  --  --  --  --  --  --  --  --  0.94                                     M --  --  --  --  --  --  --  --  --  1.04                                     W --  --  --  --  --  --  --  --  --  0.44                               KF    C 2.1 2.1 --  --  --  --  --  --  --  --                                       M 2.38                                                                               2.41                                                                     W 1.43                                                                               1.44                                                                     C 10  10  12.04                                                                              12.04                                                                              12.01                                                                              7.8 12.04                                                                              12.04                                                                              --  12.04                                    M 11.31                                                                              11.47                                                                              13.45                                                                              13.49                                                                              13.27                                                                              8.76                                                                               13.86                                                                              14.27   13.32                                    W 4.91                                                                               4.95                                                                               5.72                                                                               5.70                                                                               5.56                                                                               3.65                                                                               5.69                                                                               6.12    5.82                               LiF     --  --  --  --  --  --  --  --  --  --                                 1/2K.sub.2 O                                                                         C --  --  --  --  --  4.62                                                     M                     5.19                                                     W                     2.43                                               1/2Na.sub.2 O                                                                          --  --  --  --  --  --  --  --  12.3                                                                           7.33                                                                           4.92                                   1/2Li.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 MoO.sub.3                                                                            C --  2   0.4 0.4 0.8 0.4 0.4 0.4 0.4 0.4                                      M --  2.29                                                                               0.45                                                                               0.45                                                                               0.88                                                                               0.45                                                                               0.46                                                                               0.47                                                                               0.47                                                                               0.44                                     W --  3.39                                                                               0.15                                                                               0.65                                                                               1.27                                                                               0.64                                                                               0.65                                                                               0.70                                                                               0.67                                                                               0.66                               TiO.sub.2                                                                            C --  2   --  --  --  --  --  --  --  --                                       M --  2.29                                                                     W --  1.89                                                               1/2Nb.sub.2 O.sub.5                                                                  C 2   --  --  --  --  --  --  --  --  --                                       M 1.13                                                                               --  --  --  --  --  --  --  --  --                                       W 3.10                                                                               --  --  --  --  --  --  --  --  --                                 NdF.sub.3                                                                            C --  --  1.36                                                                               1.5 0.05                                                                               --  --  --  --  --                                       M --  --  1.52                                                                               1.68                                                                               0.01                                                         W --  --  3.10                                                                               3.41                                                                               0.02                                                                               --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1.2 0.7 1   1.5 --  3   1.2 1.2 1.2 1.2                                      M 0.68                                                                               0.40                                                                               0.56                                                                               0.84                                                                               --  1.69                                                                               0.69                                                                               0.71                                                                               0.7 0.66                                     W 2.36                                                                               1.39                                                                               1.90                                                                               2.85                                                                               --  5.62                                                                               2.27                                                                               2.44                                                                               2.34                                                                               2.32                               L.sub.T 630 760 631 637 687 710 820 835 755 629                                n.sub.2 0.67                                                                               0.68                                                                               0.66                                                                               0.66                                                                               0.72                                                                               0.69                                                                               0.75                                                                               0.73                                                                               0.69                                                                               0.64                               No.     31  32  33  34  35  36  37  38  39  40                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 18  18  18  18  18  18  18  18  18  18                                       M 9.9 9.9 9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                     W 14.73                                                                              14.66                                                                              14.70                                                                              14.66                                                                              14.74                                                                              14.79                                                                              14.69                                                                              15.02                                                                              14.91                                                                              14.80                              AlF.sub.3                                                                            C 32.98                                                                              32.98                                                                              32.98                                                                              32.98                                                                              30.98                                                                              29.98                                                                              28.98                                                                              30.98                                                                              29.48                                                                              28.48                                    M 36.48                                                                              36.56                                                                              36.48                                                                              36.98                                                                              34.27                                                                              33.16                                                                              32.06                                                                              34.27                                                                              32.61                                                                              31.50                                    W 31.94                                                                              31.80                                                                              31.88                                                                              31.79                                                                              30.01                                                                              27.31                                                                              28.91                                                                              30.61                                                                              28.89                                                                              27.70                              YF.sub.3                                                                             C 2   2   2   2   2   2   2   --  1.5 2.5                                      M 2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               --  1.66                                                                               2.77                                     W 3.36                                                                               3.35                                                                               3.36                                                                               3.95                                                                               3.37                                                                               3.37                                                                               3.35                                                                               --  2.55                                                                               4.23                               LaF.sub.3                                                                              --  --  --  --  --   -- --  --  --  --                                 1/2Al.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 1/2Y.sub.2 O.sub.3                                                                     --  --  --  --  --  --  --  --  --  --                                 1/2La.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 BaF.sub.2                                                                            C 6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                     M 7.00                                                                               7.02                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                     W 12.80                                                                              12.75                                                                              12.78                                                                              12.74                                                                              12.80                                                                              12.83                                                                              12.74                                                                              13.05                                                                              12.95                                                                              12.86                              SrF.sub.2                                                                            C 8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                     M 8.97                                                                               8.99                                                                               8.97                                                                               8.97                                                                               8.97                                                                               8.97                                                                               8.97                                                                               8.97                                                                               8.97                                                                               8.97                                     W 11.75                                                                              11.70                                                                              11.73                                                                              11.69                                                                              11.75                                                                              11.78                                                                              11.70                                                                              11.98                                                                              11.89                                                                              11.80                              CaF.sub.2                                                                            W 18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                    M 21.00                                                                              21.04                                                                              21.00                                                                              21.00                                                                              21.00                                                                              21.00                                                                              21.00                                                                              21.00                                                                              21.00                                                                              21.00                                    W 17.09                                                                              17.02                                                                              17.06                                                                              17.01                                                                              17.09                                                                              17.14                                                                              17.01                                                                              17.43                                                                              17.29                                                                              17.17                              MgF.sub.2                                                                            C --  --  --  --  2   3   4   4   4   4                                        M --  --  --  --  2.21                                                                               3.32                                                                               4.42                                                                               4.42                                                                               4.42                                                                               4.42                                     W --  --  --  --  1.44                                                                               1.95                                                                               2.86                                                                               2.93                                                                               2.91                                                                               2.89                               BaO     --  --  --  --  --  --  --  --  --  --                                 SrO     --  --  --  --  --  --  --  --  --  --                                 CaO     --  --  --  --  --  --  --  --  --  --                                 MgO     --  --  --  --  --  --  --  --  --  --                                 KF      --  --  --  --  --  --  --  --  --  --                                 NAF   C 12.4                                                                               12  12  12  12  12  12  12  12  12                                       M 13.72                                                                              13.30                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                    W 6.00                                                                               5.79                                                                               5.80                                                                               5.78                                                                               5.81                                                                               5.83                                                                               5.78                                                                               5.93                                                                               5.88                                                                               5.84                               LiF     --  --  --  --  --  --  --  --  --  --                                 1/2K.sub.2 O                                                                           --  --  --  --  --  --  --  --  --  --                                 1/2K.sub.2 O                                                                           --  --  --  --  --  --  --  --  --  --                                 1/2Li.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 MoO.sub.3                                                                            C --  --  --  0.4 0.4 0.4 0.4 0.4 --  --                                       M --  --  --  0.45                                                                               0.45                                                                               0.45                                                                               0.45                                                                               0.45                                                                               --  --                                       W --  --  --  0.66                                                                               0.66                                                                               0.67                                                                               0.66                                                                               0.68                                                                               --  --                                 TiO.sub.2                                                                            C --  --  0.44                                                                               --  --  --  --  --  0.4 0.4                                      M --  --  0.45                                                                               --  --  --  --  --  0.45                                                                               0.45                                     W --  --  0.37                                                                               --  --  --  --  --  0.37                                                                               0.37                               1/2Nb.sub.2 O.sub.5                                                                  C --  0.4 --  --  --  --  --  --  --  --                                       M --  0.22                                                                               --  --  --  --  --  --  --  --                                       W --  0.61                                                                               --  --  --  --  --  --  --  --                                 NdF.sub.3                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2                                      M 0.66                                                                               0.69                                                                               0.66                                                                               0.66                                                                               0.66                                                                               0.66                                                                               0.66                                                                               0.66                                                                               0.66                                                                               0.66                                     W 2.33                                                                               2.32                                                                               2.32                                                                               2.32                                                                               2.33                                                                               2.33                                                                               2.32                                                                               2.37                                                                               2.36                                                                               2.34                               L.sub.T 600 632 610 605 600 597 580 621 592 602                                n.sub.2 0.63                                                                               0.66                                                                               0.65                                                                               0.67                                                                               0.65                                                                               0.64                                                                               0.63                                                                               0.62                                                                               0.63                                                                               0.64                               No.     41  42  43  44  45  46  47  48  49  50                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 18  18  18  18  18  18  18  18  18  18                                       M 9.96                                                                               9.96                                                                               9.96                                                                               9.98                                                                               10.00                                                                              9.98                                                                               9.98                                                                               9.98                                                                               9.98                                                                               10.00                                    W 14.75                                                                              14.65                                                                              14.34                                                                              14.47                                                                              14.59                                                                              14.78                                                                              14.48                                                                              14.64                                                                              14.86                                                                              14.19                              AlF.sub.3                                                                            C 27.98                                                                              27.48                                                                              27.48                                                                              27.48                                                                              27.48                                                                              28.48                                                                              28.48                                                                              28.48                                                                              28.48                                                                              28.48                                    M 30.95                                                                              30.40                                                                              30.40                                                                              30.46                                                                              30.54                                                                              31.59                                                                              31.59                                                                              31.59                                                                              31.59                                                                              31.66                                    W 27.12                                                                              26.47                                                                              25.89                                                                              26.01                                                                              26.36                                                                              27.68                                                                              27.10                                                                              27.42                                                                              27.65                                                                              26.58                              YF.sub.3                                                                             C 3   3.5 3.5 3.5 3.0 2   2   2   2   2                                        M 3.32                                                                               3.87                                                                               3.87                                                                               3.88                                                                               3.34                                                                               2.22                                                                               2.22                                                                               2.22                                                                               2.22                                                                               2.23                                     W 5.05                                                                               5.86                                                                               5.93                                                                               5.89                                                                               5.00                                                                               3.38                                                                               3.30                                                                               3.34                                                                               3.38                                                                               3.24                               LaF.sub.3                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Al.sub.2 O.sub.3                                                                  C --  --  --  --  --  0.5 0.5 0.5 0.5 0.5                                      M --  --  --  --  --  0.28                                                                               0.28                                                                               0.28                                                                               0.28                                                                               0.28                                     W --  --  --  --  --  0.29                                                                               0.29                                                                               0.29                                                                               0.30                                                                               0.28                               1/2Y.sub.2 O.sub.3                                                                     --  --  --  --  --  --  --  --  --  --                                 1/2La.sub.2 O.sub.3                                                                    --  --  --  --  0.5 --  --  --  --  --                                                         0.28                                                                           0.90                                                   BaF.sub.2                                                                            C 6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                     M 7.00                                                                               7.00                                                                               7.00                                                                               7.02                                                                               7.04                                                                               7.02                                                                               7.02                                                                               7.02                                                                               7.02                                                                               7.04                                     W 12.81                                                                              12.73                                                                              12.45                                                                              12.80                                                                              12.68                                                                              12.84                                                                              12.58                                                                              12.72                                                                              12.86                                                                              12.33                              SrF.sub.2                                                                            C 8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                     M 8.97                                                                               8.97                                                                               8.97                                                                               8.99                                                                               9.02                                                                               9.00                                                                               9.00                                                                               9.00                                                                               9.00                                                                               9.02                                     W 11.76                                                                              11.68                                                                              11.43                                                                              11.75                                                                              11.64                                                                              11.79                                                                              11.55                                                                              11.68                                                                              11.81                                                                              11.33                              CaF.sub.2                                                                            C 18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                    M 21.00                                                                              21.00                                                                              21.00                                                                              21.04                                                                              21.10                                                                              21.05                                                                              21.05                                                                              21.05                                                                              21.05                                                                              21.10                                    W 17.11                                                                              17.00                                                                              16.63                                                                              17.09                                                                              16.93                                                                              17.15                                                                              16.79                                                                              16.99                                                                              17.17                                                                              16.46                              MgF.sub.2                                                                            C 4   4   4   4   4   4   4   2   2                                            M 4.42                                                                               4.42                                                                               4.42                                                                               4.43                                                                               4.45                                                                               4.44                                                                               2.22                                                                               2.22                                                                               2.22                                                                               --                                       W 2.88                                                                               2.86                                                                               2.80                                                                               2.87                                                                               2.85                                                                               2.88                                                                               1.41                                                                               1.43                                                                               1.44                                   BaO   C --  --  --  --  --  --  2   --  --  4                                        M                         2.22        4.44                                     W                         3.48        6.81                               SrO   C --  --  --  --  --  --  --  2                                                M                             2.22                                             W                             2.38                                       CaO   C --  --  --  --  --  --  --  --  2   --                                       M                                 2.22                                         W                                 1.30                                   MgO     --  --  --  --  --  --  --  --  --  --                                 KF    C --  --  12  2   2   2   2   2   2   2                                        M --  --  13.27                                                                              2.22                                                                               2.22                                                                               2.22                                                                               2.22                                                                               2.22                                                                               2.22                                                                               2.22                                     W --  --  7.82                                                                               1.34                                                                               1.33                                                                               1.34                                                                               1.32                                                                               1.33                                                                               1.35                                                                               1.29                               NaF   C 12  12  --  10  10  10  10  10  10  10                                       M 13.27                                                                              13.27                                                                              --  11.09                                                                              11.12                                                                              11.09                                                                              11.09                                                                              11.09                                                                              11.09                                                                              11.12                                    W 5.82                                                                               5.78                                                                               --  9.84                                                                               4.80                                                                               4.86                                                                               4.76                                                                               4.81                                                                               4.87                                                                               4.66                               LiF     --  --  --  --  --  --  --  --  --  --                                 1/2K.sub.2 O                                                                           --  --  --  --  --  --  --  --  --  --                                 1/2Na.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 1/2Li.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 MoO.sub.3                                                                            C --  0.4 0.4 --  --  0.4 0.4 0.4 0.4 --                                       M --  0.45                                                                               0.45                                                                               --  --  0.44                                                                               0.44                                                                               0.44                                                                               0.94                                                                               --                                       W --  0.66                                                                               0.65                                                                               --  --  0.67                                                                               0.65                                                                               0.66                                                                               0.67                                                                               --                                 TiO.sub.2                                                                            C 0.4 --  --  --  --  --  --  --  --  --                                       M 0.45                                                                               --  --  --  --  --  --  --  --  --                                       W 0.37                                                                               --  --  --  --  --  --  --  --  --                                 1/2Nb.sub.2 O.sub.5                                                                  C --  --  --  0.4 0.4 --  --  --  --  0.4                                      M --  --  --  0.22                                                                               0.22                0.22                                     W --  --  --  0.61                                                                               0.61                                                                               --  --  --  --  0.59                               NdF.sub.3                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2                                      M 0.66                                                                               0.66                                                                               0.66                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                     W 2.33                                                                               2.31                                                                               2.26                                                                               2.33                                                                               2.31                                                                               2.34                                                                               2.29                                                                               2.31                                                                               2.34                                                                               2.24                               L.sub.T 610 613 627 615 641 605 631 624 619 662                                n.sub.2 0.65                                                                               0.67                                                                               0.63                                                                               0.64                                                                               0.68                                                                               0.65                                                                               0.67                                                                               0.67                                                                               0.66                                                                               0.68                               No.     51  52  53  54  55  56  57  58  59  60                                 __________________________________________________________________________     1/2P.sub.2 O.sub.5                                                                   C 18  18  18  18  18  18  18  18  18  18                                       M 10.00                                                                              10.00                                                                              10.00                                                                              9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                                                               9.96                                     W 14.51                                                                              14.83                                                                              14.94                                                                              14.94                                                                              15.01                                                                              15.45                                                                              14.15                                                                              14.16                                                                              14.29                                                                              14.12                              AlF.sub.3                                                                            C 28.48                                                                              28.48                                                                              28.48                                                                              32.98                                                                              32.98                                                                              32.98                                                                              32.98                                                                              32.98                                                                              32.98                                                                              32.98                                    M 31.66                                                                              31.66                                                                              31.66                                                                              36.48                                                                              36.48                                                                              36.48                                                                              36.48                                                                              36.48                                                                              36.48                                                                              36.48                                    W 27.18                                                                              27.77                                                                              27.98                                                                              32.43                                                                              32.55                                                                              33.49                                                                              30.70                                                                              30.70                                                                              30.99                                                                              30.10                              YF.sub.3                                                                             C 2   2   2   2   2   2   2   2   2   2                                        M 2.23                                                                               2.23                                                                               2.23                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                                                               2.21                                     W 3.31                                                                               3.39                                                                               3.41                                                                               3.41                                                                               3.43                                                                               3.53                                                                               3.24                                                                               3.23                                                                               3.27                                                                               3.22                               LaF.sub.3                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Al.sub.2 O.sub.3                                                                  C 0.5 0.5 0.5 --  --  --  --  --  --  --                                       M 0.28                                                                               0.28                                                                               0.28                                                                 W 0.29                                                                               0.30                                                                               0.30                                                                               --  --  --  --  --  --  --                                 1/2Y.sub.2 O.sub.3                                                                     --  --  --  --  --  --  --  --  --  --                                 1/2La.sub.2 O.sub.3                                                                    --  --  --  --  --  --  --  --  --  --                                 BaF.sub.2                                                                            C 6.33                                                                               6.33                                                                               6.33                                                                               --  6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                                                               6.33                                     M 7.04                                                                               7.04                                                                               7.04                                                                               --  7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                                                               7.00                                     W 12.06                                                                              12.89                                                                              12.98                                                                              --  13.04                                                                              13.42                                                                              12.31                                                                              12.30                                                                              12.42                                                                              12.26                              SrF.sub.2                                                                            C 8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               --  8.11                                                                               8.11                                                                               8.11                                                                               8.11                                                                               8.11                                     M 9.00                                                                               9.00                                                                               9.00                                                                               8.97                                                                               --  8.97                                                                               8.97                                                                               5.65                                                                               8.97                                                                               8.97                                     W 11.57                                                                              11.83                                                                              11.92                                                                              11.92                                                                              --  12.32                                                                              11.30                                                                              11.29                                                                              11.40                                                                              11.26                              CaF.sub.2                                                                            C 18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              18.98                                                                              --  18.98                                                                              18.98                                                                              14.98                                                                              12.98                                    M 21.05                                                                              21.05                                                                              21.05                                                                              21.00                                                                              21.00                                                                              --  21.00                                                                              21.00                                                                              16.58                                                                              14.36                                    W 16.84                                                                              17.20                                                                              17.33                                                                              17.33                                                                              17.33                                                                              --  16.43                                                                              16.42                                                                              16.58                                                                              16.38                              MgF.sub.2                                                                            --                                                                               --  --  --  --  --  --  --  --  --                                     BaO   C --  --  --  6.33                                                                               --  --  2   --  --  --                                       M --  --  --  7.00                                                                               --  --  2.21                                                                               --  --  --                                       W --  --  --  11.35                                                                              --  --  3.40                                                                               --  --  --                                 SrO   C 4   --  --  --  8.11                                                                               --  --  3   --  --                                       M 4.44                                                                               --  --  --  8.97                                                                               --  --  3.32                                                                               --  --                                       W 9.71                                                                               --  --  --  9.58                                                                               --  --  3.44                                                                               --  --                                 CaO   C --  4   --  --  --  18.98                                                                              --  --  4   6                                        M --  4.44                                                                               --  --  --  21.00                                                                              --  --  4.42                                                                               6.64                                     W --  2.60                                                                               --  --  --  12.87                                                                              --  --  2.51                                                                               3.72                               MgO   C --  --  4   --  --  --  --  --  --  --                                       M --  --  4.44                                                                               --  --  --  --  --  --  --                                       W --  --  1.89                                                                               --  --  --  --  --  --  --                                 KG    C 2   2       --  --  --  --  --  --  --                                       M 2.22                                                                               2.22                                                                               2.22                                                                               --  --  --  --  --  --  --                                       W 1.32                                                                               1.35                                                                               1.36                                                                               --  --  --  --  --  --  --                                 NaF   C 10  10  10  12  12  12  12  12  12  12                                       M 11.12                                                                              11.12                                                                              11.12                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                                                                              13.27                              LiF   W 4.77                                                                               4.88                                                                               4.91                                                                               5.89                                                                               5.92                                                                               6.09                                                                               5.59                                                                               5.58                                                                               5.64                                                                               5.57                               1/2K.sub.2 O                                                                           --  --  --  --  --  --  --  --  --  --                                 1/2Na.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 1/2Li.sub.2 O                                                                          --  --  --  --  --  --  --  --  --  --                                 MoO.sub.3                                                                            C --  --  --  --  --  --  0.4 0.4 0.4 0.4                                      M --  --  --  --  --  --  0.44                                                                               0.44                                                                               0.44                                                                               0.44                                     W --  --  --  --  --  --  0.64                                                                               0.64                                                                               0.64                                                                               0.64                               TiO.sub.2                                                                            C --  --  --  0.4 0.4 0.4 --  --  --  --                                       M --  --  --  0.44                                                                               0.44                                                                               0.44                                                                               --  --  --  --                                       W --  --  --  0.37                                                                               0.38                                                                               0.39                                                                               --  --  --  --                                 1/2Nb.sub.2 O.sub.5                                                                  C 0.4 0.4 0.4 --  --  --  --  --  --  --                                       M 0.22                                                                               0.22                                                                               0.22                                                                               --  --  --  --  --  --  --                                       W 0.60                                                                               0.62                                                                               0.62                                                                               --  --  --  --  --  --  --                                 NdF.sub.3                                                                              --  --  --  --  --  --  --  --  --  --                                 1/2Nd.sub.2 O.sub.3                                                                  C 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2                                      M 0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                                                               0.67                                     W 2.27                                                                               2.34                                                                               2.36                                                                               2.36                                                                               2.37                                                                               2.44                                                                               2.24                                                                               2.24                                                                               2.26                                                                               2.23                               L.sub.T 643 640 637 722 750 832 670 710 712 723                                n.sub.2 0.68                                                                               0.66                                                                               0.64                                                                               0.71                                                                               0.72                                                                               0.74                                                                               0.68                                                                               0.68                                                                               0.69                                                                               0.70                               __________________________________________________________________________      C: Cationic %                                                                  M: Mol %                                                                       W: Weight %                                                              

For the preparation of the fluorophosphate-base laser glasses of the present invention as shown in the Table above the components are sufficiently mixed, melted, stirred and refined over a period of about 2 to 10 hrs. at about 1,000° C. in a ceramic crucible or a fire-resistant metal crucible, and the resulting melt was molded. As a result, the glass could be obtained as a large-sized mass without devitrification in spite of the fact that the amount of the glass forming oxides is very small.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. 

What is claimed is:
 1. A stable fluorophosphate-base laser glass having a non-linear refractive index coefficient of 0.5 to 0.7 × 10⁻¹³ e.s.u. and a liquid phase temperature of 550° to 750° C. consisting essentially of 5 to 25% 1/2P₂ O₅ and the remainder being a mixture of fluorides of the metals Al, Ba, Sr and Ca, and 0 to 25% fluorides of Na, K and Li and 0 to 5% of each of the fluorides of Y, La and Mg, and 0.01 to 3% of at least one laser oscillation component selected from the group consisting of 1/2 Er₂ O₃, 1/2 Eu₂ O₃ and 1/2Nd₂ O₃ incorporated into said glass, said percentages being cationic %, said glass not containing any glass forming component which would adversely affect laser oscillation efficiency thereof.
 2. The fluorophosphate-base laser glass as claimed in claim 1, further including 0.1 to 4 cationic % MoO₃ +TiO₂ +1/2Nb₂ O₅ as components for preventing occurrence of solarization.
 3. The fluorophosphate-base laser glass as claimed in claim 1, wherein said laser oscillation component is 1/2Nd₂ O₃.
 4. A stable fluorophosphate-base laser glass having a non-linear refractive index coefficient of 0.5 to 0.7 × 10⁻¹³ e.s.u. and a liquid phase temperature of 550° to 750° C. consisting essentially of 5 to 25% 1/2P₂ O₅, 20 to 35% AlF₃, 0 to 5% YF₃, 22 to 55% BaF₂ + SrF₂ + CaF₂ + MgF₂, 0 to 25% NaF+LiF+KF and 0.01 to 3% of at least one laser oscillation component selected from the group consisting of 1/2 Er₂ O₃, 1/2Eu₂ O₃ and 1/2Nd₂ O₃, said percentages being cationic %, said glass not containing any glass forming component which would adversely affect laser oscillation efficiency thereof.
 5. The fluorophosphate-base laser glass as claimed in claim 4, further including 0.1 to 4 cationic % MoO₃ +TiO₂ +1/2Nb₂ O₅ as components for preventing the occurrence of solarization.
 6. The fluorophosphate-base laser glass as claimed in claim 4, wherein said laser oscillation component is 1/2Nd₂ O₃.
 7. A stable fluorphosphate-base laser glass having a non-linear refractive index coefficient of 0.5 to 0.7 × 10⁻¹³ e.s.u. and a liquid phase temperature of 550° to 750° C. consisting essentially of 5 to 25% 1/2P₂ O₅, 20 to 35% AlF₃, 0 to 5% YF₃, 22 to 55% BaF₂ +SrF₂ +CaF₂ +MgF₂ with 2 to 12% BaF, 4 to 18% SrF₂, 15 to 28% CaF₂ and 0 to 5% MgF₂, 0 to 25% NaF+LiF+KF and 0.01 to 3% of at least one laser oscillation component selected from the group consisting of 1/2 Er₂ O₃, 1/2 Eu₂ O₃ and 1/2Nd₂ O₃, said percentages being cationic %, said glass not containing any glass forming component which would adversely affect laser oscillation efficiency thereof.
 8. The fluorophosphate-base laser glass as claimed in claim 7, further comprising 0.1 to 4 cationic % MoO₃ +TiO₂ +1/2Nb₂ O₅ as components for preventing the occurrence of solarization.
 9. The fluorophosphate-base laser glass as claimed in claim 7, wherein said laser oscillation component is 1/2Nd₂ O₃. 